[lldb-dev] [LLVMdev] Reusing LLVM Mips instruction info in lldb

[Daniel Sanders]

> Would you have any objections to making lib/Target/*/MCTargetDesc/*MCTargetDesc.h public?

One worry that springs to mind is how easy it is to renumber the enum values used by the opcodes. If these numbers are public it will be hard to have stable releases that add new instructions.

From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Reid Kleckner
Sent: 24 February 2015 21:40
To: Eric Christopher
Cc: Keno Fischer; lldb-dev; LLVM Developers Mailing List
Subject: Re: [LLVMdev] [lldb-dev] Reusing LLVM Mips instruction info in lldb

On Tue, Feb 24, 2015 at 1:09 PM, Eric Christopher <echristo at gmail.com<mailto:echristo at gmail.com>> wrote:

On Tue Feb 24 2015 at 1:03:43 PM Keno Fischer <kfischer at college.harvard.edu<mailto:kfischer at college.harvard.edu>> wrote:
Hello everyone,

in http://reviews.llvm.org/D7696 bhushan added a mips64 UnwindAssembly plugin (a plugin that looks at assembly code to find out how to unwind the stack frame). Since I was about to write such a plugin (though for mips32) myself, I used it as a starting point for a slightly different implementation [1], replacing hard coded instruction encodings by calls to the LLVM disassembler. This works great, except that the necessary header that defines the enum to interpret the opcode in MCInst is generated by llvm during the build process using tablegen and is hence not a public header. What is the best solution to be able to use this information from lldb (which needs to be able to build against a prebuilt copy of LLVM)? Would it make sense to move the appropriate .td to llvm/include/Target/Mips, so lldb could re-tablegen it and obtain the same header (I assume tablegening is deterministic?)?

Ugh no. (Though yes, it is deterministic afaik).

Does anybody see any other good solutions?


Develop an interface that works and have lldb use that? Might need to change things to have certain bits be made public if necessary, but I'd want more details there.

Would you have any objections to making lib/Target/*/MCTargetDesc/*MCTargetDesc.h public?

It seems pretty useless to expose a disassembly interface that can't tell you anything interesting about the instruction.
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